This page has no translation to Français yet. The original English version is below. If you’d like to help, great! See how to translate a documentation page in the contribution guide.
Note This is a web-version of a tutorial chapter embedded right into the XOD IDE. To get a better learning experience we recommend to install the desktop IDE or start the browser-based IDE, and you’ll see the same tutorial there.


Screenshot of 208-accumulator

Let’s make a device which helps us in adding numbers. We will learn how to memorize values and update them.

The XOD standard library contains a buffer node which memorizes the input value when it receives a pulse.

To make some calculations and apply them to a stored value we should make a loop from the buffer output to the calculations and back to the buffer input.

To avoid limitless calculations and make it possible to reset the buffer we need a select node. It feeds the calculation result to the buffer node on a pulse.

In this example we’re using the add node, but the calculation may be arbitrary complex.

Exercise #

Examine how the input value and pulses affect the stored result.

  1. Upload the program.
  2. Change the tweak-number value.
  3. Send pulse from the “ADD” node.
  4. Repeat the second and third steps a few times.
  5. Send pulse from “RESET”.

Replace tweak nodes with a coin acceptor and button to make a ticket system or photo booth.

Found a typo or mistake? Want to improve the text? Edit this page on GitHub and open a pull request. If you have a complex proposal or you want to discuss the content, feel free to start a new thread on XOD forum.